Auxiliary devices are often attached to printing presses, such as sheetfed printing presses, to enhance the quality of the printing by eliminating problems that are inherent in printing operations. For example, to decrease printing offset, i.e., the blurring of ink caused by subsequently stacked sheets, it has been found useful to coat a printed sheet with powder after inking the sheet. Accordingly, one such auxiliary device comprises a roller-type powder sprayer. In these devices, a roller is rotated to discharge a metered amount of the powder onto the sheet. Electrostatic means may be employed to facilitate complete removal of powder from the roller at the zone of the discharge. The powder deposited on each sheet further acts to maintain sheet separation, which aids in the ink drying process.
Such powder sprayers may be further combined with another auxiliary device that automatically supplies powder to the sprayer. Two such auxiliary powder sprayers with supply systems are described in U.S. Pat. Nos. 5,083,710 and 5,213,271, assigned to the same assignee as the present application.
Another common auxiliary device that is installed on presses consists of a blanket washer for cleaning accumulated foreign matter off of blanket cylinders and plate cylinders. Such accumulated foreign matter typically includes dried ink, ink build-up, paper, lint and the like, and must be removed in order to maintain high-quality printing. To remove the foreign matter, printing presses are often outfitted with auxiliary cleaning systems such as those disclosed in U.S. Pat. Nos. 5,010,819, 5,109,770, 5,277,111 and 4,015,307, assigned to the same assignee as the present application.
In addition to blanket washers, other auxiliary devices can include one or more dryers, an air knife, and/or an air evacuator. These devices generally are installed on printing presses to speed the chemical bonding process (i.e., the drying and curing) of inks deposited on a sheet, which allows faster printing speeds to be run and produces with consistent inking. While the many auxiliaries thus enhance the printing operation, each of the devices have individual parameters which must be set according to the specific job being run. In addition, once set, the parameters must occasionally be adjusted to "fine-tune" their performance, such as to compensate for variations in temperature and humidity, to optimize the printing operation.
By way of example, certain types of inks and types of paper require more powder to prevent offset than do other types of inks and types of paper. However, it is desirable to use only the minimum amount of powder on each sheet that acceptably prevents offset, since excess powder tends to spread to undesirable areas. Moreover, powder that does remain on the sheet must ultimately be removed from the sheet at a later time, so again it is desirable to discharge only the necessary amount to make removal less burdensome.
Thus, each time a different job is run, the press operator must set the operating parameters of the auxiliary devices at appropriate values for the particular paper and ink combination being run. For the sprayer, the press operator typically enters an appropriate value for the powder discharge, which typically is entered as a percentage of maximum sprayer output capacity. Of course, depending on current conditions such as temperature and humidity, the discharge of powder may be further modified from a known starting value for that ink and paper combination. Accordingly, the press operator must make adjustments to occasionally compensate for these and other varying conditions based on periodic examinations of the printed product.
Similar parameters must be entered and subsequently adjusted for each auxiliary device every time a different job is being run. However, printing presses are physically large mechanisms. As a result, in order to adjust the parameters of the several auxiliary devices, an operator must walk to the control panel of each device and make the adjustment. Similarly, the operator must periodically inspect the control panels to obtain certain information as to the status of the devices.
Moreover, each new printing run typically requires the operator to adjust several of the auxiliary device parameters. The operator individually sets the values at the approximate settings required for a particular job based on prior experience, or by consulting a reference manual or the like where the values for similar jobs on the same press have previously been recorded.
In short, the present way of setting operating parameters is time-consuming, depends on the reliability of the press operator, and results in inconsistent quality over several jobs.